Altering the amount of time your camera's shutter remains open increases the amount of light reaching the sensor. an extended exposure, when used well, makes creative motion and blurring effects possible.
Long exposures with the camera mounted on a sturdy tripod lend themselves well to capturing motion. This is no better illustrated than when shooting light trails in low light. Exposures slower than around 1/4 of a second, but ideally in excess of a few seconds, allow light motion to be captured. Other creative possibilities include using a torch to ‘paint' with light or produce ‘light writing'.
Take control of your shutter speed settings and get experimenting.